In combustion systems it is desirable to achieve low emissions (NOx). These emissions are highly dependent on the extent of the mixing of fuel with an oxidant. An improved mixing of the fuel with the oxidant brings the combustion system closer to an ideally mixed system and therefore reduces the emissions (NOx).
To improve mixing of the fuel with the oxidant in prior art combustion systems fuel simply is injected into a cross flow of air through simple holes upstream of the combustion flame. Thereby, the mixing is driven by the flow patterns and the level of turbulence. Nevertheless, the mixing achieved with this approach is not satisfactory. Furthermore, fuel injection in the prior art is known in which for an improvement of the mixing of fuel with the oxidant the fuel is injected into a chamber of a combustion apparatus, wherein a swirl is imparted to the fuel by an injection device. This prior art injection device comprises an injection duct in combination with a separate structure inserted into the injection duct. The fabrication of a corresponding injection device is complex and costly.